Submission #390420

#	Time	Username	Problem	Language	Result	Execution time	Memory
390420		Drew_	Aliens (IOI16_aliens)	C++17	0 / 100	1 ms	204 KiB

aliens

#include "aliens.h"
#include <vector>
#include <iostream>
#include <algorithm>
#include <cassert>
using namespace std;

#define ll long long
#define pb push_back
#define ii pair<int, int>
#define f1 first
#define s2 second

vector<ii> interval;

//cost for interval [i, j], assuming interval [0, i-1] have been fulfilled
inline ll getCost(int i, int j)
{
	ll res = 1LL * (interval[j].s2 - interval[i].f1 + 1) * (interval[j].s2 - interval[i].f1 + 1);
	if (i)
	{
		if (interval[i-1].s2 >= interval[i].f1)
			res -= 1LL * (interval[i-1].s2 - interval[i].f1 + 1) * (interval[i-1].s2 - interval[i].f1 + 1);
	}
	return res;
}

vector<ll> dp[2];
inline void dnc(int k, int l, int r, int optL, int optR)
{
	if (l > r)
		return;

	int mid = (l + r) / 2;

	ll optVal = 1e18;
	int optIdx = -1;
	for (int i = optL; i <= mid && i <= optR; ++i)
	{
		ll val = (i ? dp[(k+1) & 1][i-1] : 0) + getCost(i, mid);
		if (optVal > val)
		{
			optVal = val;
			optIdx = i;
		}
	}

	dp[k&1][mid] = optVal;
	dnc(k, l, mid-1, optL, optIdx-1);
	dnc(k, mid+1, r, optIdx+1, optR);
}


long long take_photos(int n, int m, int k, std::vector<int> r, std::vector<int> c) {
	vector<ii> v(n);
	for (int i = 0; i < n; ++i)
		v[i] = {min(r[i], c[i]), max(r[i], c[i])};
	sort(v.begin(), v.end(), [](const ii &x, const ii &y){
		return x.f1 < y.f1 || (x.f1 == y.f1 && x.s2 > y.s2);
	});

	interval.pb(v[0]);
	for (int i = 1; i < n; ++i)
	{
		if (interval.back().f1 <= v[i].f1 && v[i].s2 <= interval.back().s2)
			continue;
		interval.pb(v[i]);
	}

	for (int i = 0; i+1 < interval.size(); ++i)
		assert(interval[i].f1 < interval[i+1].f1 && interval[i].s2 < interval[i+1].s2);

	dp[0].resize(interval.size());
	dp[1].resize(interval.size());


	for (int i = 0; i < interval.size(); ++i)
		dp[1][i] = getCost(0, i);

	for (int j = 2; j <= k; ++j)
		dnc(j, 0, interval.size() - 1, 0, interval.size() - 1);

    return dp[k & 1].back();
}

Compilation message (stderr)

aliens.cpp: In function 'long long int take_photos(int, int, int, std::vector<int>, std::vector<int>)':
aliens.cpp:70:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   70 |  for (int i = 0; i+1 < interval.size(); ++i)
      |                  ~~~~^~~~~~~~~~~~~~~~~
aliens.cpp:77:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   77 |  for (int i = 0; i < interval.size(); ++i)
      |                  ~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 4
• Subtask 2: 0 / 12
• Subtask 3: 0 / 9
• Subtask 4: 0 / 16
• Subtask 5: 0 / 19
• Subtask 6: 0 / 40